It is known to prepare tetrahydrocarbylammonium tetrahydridoborates by reaction of tetrahydrocarbylammonium salts with an alkali metal borohydride, however, by such process yields are low and the product is contaminated with the alkali metal salt by-products.
In order to improve yields and product quality, it has been proposed to react a tetrahydrocarbylammonium hydroxide with an alkali metal borohydride in an aqueous solution followed by drying the reaction mixture and extracting the dry solid mix of products with ethyl alcohol to remove the alkali metal hydroxide formed. Better yields are obtained with this approach but many process steps have been added and the possibility for hydrolysis of the borohydride radical exists.
Other known methods for the preparation of this class of products involve the use of more expensive materials such as LiAlH.sub.4 or MgB.sub.2 or the use of more complicated and thus, costly process methods.
It is an object of this invention to provide a simple economic process for the preparation of tetrahydrocarbylammonium tetrahydridoborates in high purity or good yields, with good product quality and with a minimum of processing steps.
The tetrahydrocarbylammonium tetrahydridiborates are a known class of compounds and are known to be useful in a wide variety of chemical reactions as reducing agents such as for aldehydes and ketones to the corresponding acids and aldehydes, reduction of acid chlorides to the corresponding alcohols, reduction of primary and secondary amides to the corresponding amines, reduction of organic disulfides to the corresponding mercaptans, and reduction of anhydrides. Generally, these materials may be used for the same general class of reactions as known to be useful for the well known alkali metal borohydrides including in addition to the above-mentioned reduction reactions, the halogenation under solvolytic conditions of secondary and tertiary alkyl halides which are capable of forming stable carbonium ions to the corresponding hydrocarbons, demercuriation reactions, and a variety of other organic and inorganic reactions. For some applications a high purity product is required or desired.